checkpatch: Update alignment check

Parenthesis alignment doesn't correctly check an existing line after an
inserted or modified line with an open parenthesis.

Fix it.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>